docs(python): Extend docstring examples for asof_join

[NedJWestern]

See #9045. I'm not sure which country, if any, was used for the original example, but Germany seems close. I haven't included examples for by_left and by_right as it doesn't seem necessary.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.39%. Comparing base (56dda21) to head (24c0576).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15810      +/-   ##
==========================================
- Coverage   80.40%   80.39%   -0.01%     
==========================================
  Files        1264     1264              
  Lines      165423   165423              
==========================================
- Hits       133011   132996      -15     
- Misses      32412    32427      +15     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[MarcoGorelli]

Nice, good to have this example

If you ran it locally and it renders fine, then the content looks good to me